Harmonic producer



'June 24,1930. R. s. OHL 1,765,606

' HARMONIC PRODUCER Filed 001;. 29 1926 AAAAAAI'A I N VEN TOR.

Z255. OM BY a V i ATTORNEY Patented June 24, 1930 UNITED STATES :PATENT OFFICE BUSEI|L S. OHL, OF NEW YORK,. N. Y., ASSIGNOR '10 AMERICAN TELEPHONE AND TELEGRAPH COMPANY,.A COB-BORAT ION OF NEW YORK IEIIALR.INIIOI|.\'I'IG PRODUCER r Application filed October 29, 1926. Serial No. 145,062.

This invention relates to harmonic producers, and particularly to arrangements for producing any desired odd or even harmonic of a fundamental frequency, to the exclusion of all other harmonics of the fundamental frequency. v

In high'freq uency transmission systems in which an osclllator, is employed, to which a piezo-electric crystal is connected to control the frequency of the oscillations sustained within-very narrow limits, it is very often necessary to couple the oscillator to one or more harmonic producers to multiply 0 ducing either 0 I gral va ue.

the fre uency of the oscillator by some intethe oscillator to increase the level of energy at the same time that multiplication in frequency takes place. In this invention, it is proposed to rovide a system for prodd harmonics, such as the third, fifth and seventh harmonics, etc., or

' even harmonics, such as the second, fourth and sixth harmonics, etc., of some fundamental frequency, and thereafter to select.

and transmit any desired odd or even harmonic, to the exclusion of all other odd or even harmonics. It is accordingly one of theobjects of this invention to so relate an oscillator to 3 a harmonic producer that either odd or even harmonics of the frequency of the oscillator will be produced by the system.

It is another object of this invention to so relate an oscillator of fundamental freqllllency to one or more harmonic producers, t at a plurality of odd harmonics, or a plurality of even harmonics, may be produced and to further select and transmit a desire odd or even harmonic to the exclusion of all other harmonics.

While the invention, will be pointed out with particularity in the appended claim, the invention itself, both as to its further objects and features, will be better understood from the detailed description hereinafter following, when read in connection with the accompanying drawing, in which Fi re 1 shows a push-pull oscillator, to w ich a piezo-electric device is connected, coupled to a push-pull harmonic producer so arranged Amplifiers are also coupled to 'is shown a push-pull oscillator which comprises two three-element thermionic tubes V and V each having a filament, a grid and a plate, the filaments of which are heated to an electron-emitting temperature by a common battery. The tubes V and V are preferably similar and equal in their structure and characteristics, and may obviously be replaced by a single duplex tube having a single filament, two grids and two plates. Connected between the grids and the filaments of the three-element thermionic tubes are resistances R and R respectively. Each resistance maintains the grld of the come sponding vacuum tube at a suitable negative potential with respect to the filament. A piezo-electric device is connected to the grids of the thermionic tubesV and V This piezo-electric device comprises a piezo-electric crystal PE which vibrates freely'between a pair of conductive electrodes P and -P. This piezo-electric device maintains the frequency of oscillations sustained by the pushpull oscillator constant within very narrow limits. It is to be understood, however, that any means familiar to the art may be employed to vary the vibratory period of the piezo-electric device in order to efl'ect a corresponding variation in the fre uenc of the oscillations sustained by the us -pu1l' oscillator. A battery B su plies t e necessary" space potential for t e lates of the vacuum tubes V and V throug inductances L and L respectively. A variable condenser D bridges inductances L and L thereby providing a local circuit which has 'no reactance, or substaiitiall negligible reo. and 0. (shown in dotted lines), respectively, existin between the plate and grid electrodes of t ese vacuum tubes.

The oscillations of the oscillator, controlled as to frequency by means of the piezoelectric device, are transmitted to the harmonic-producer. This'harmonic roducer is shown to comprise another dup ex system having two three-element thermionic tubes V and V each also having a filament, a grid and a plate, the filaments of which are also heated to an electron-emitting temperature by a common battery. These tubes may also 7 be similar and equal in their structure and characteristics, and may also be replaced by .a single duplex tube having a single filament two grids and two plates. The grid an filament of the vacuum tube V are connected to a resistance R and the grid and time constants for the input circuits of the vacuum tubes V and V respectively. Condensers C and C are employed to prevent the transmission of the first harmonic or fundamental frequency to the output circuits. A battery B supplies the necessary space potential for the plates of the vacuum tubes V and V When a switch S isthrown so as to close contact w, the plates of the vacuum tubes V and V are effectively in parallel relationship with each other, and the potential of the battery B is supplied to these plates through an inductance L Yet, when the switch S is thrown so as to close contact I), the output circuits of the vacuum tubes V and V are effectively in push-pull relationship with each other, and the lpotential of the battery B is suppliedto t e plates of the vacuum tubes V and V throu h in nder i may be so a in building ductances L and L respectively. certain conditions, the winding; arranged as to assist winding up oscillations, and, under other conditions,

the winding L ma be so arranged as to buck winding L he inductances L, and L, are coupled to an inductance L the inductance L being connected to the leads or conductors M of an out ut circuit.

I When the switch S c oses contact a, the plates of the vacuum tubes V, and V; are in parallel relationship with each other. Even harmonics of the fundamental freuency are produced, the odd harmonics and t e fundamental frequency being neutralized and rendered otherwlse substantlally inefiective by virtue of their resence in two conditions which are in p ase opposition. A variable condenser D may then be manipulated to co-operate with the inductances L, l

and L so as to provide a locally tuned circuit which has substantially no reactance at any one of the even harmonics. The selected even harmonic will then betransmitted to the inductance L and to the output circuit connected to the leads or conductors M, to the exclusion of all other even harmonics.

When the'switch S closes contact I), the output circuits of the vacuum tubes V and V are then effectively in push-pull arrangement, and consequently a plurality of odd harmonics will be produced by manipulating the variable condenser D Any one of the odd harmonics may be selected and transmitted to the tuned circuit connected to the leads or conductors M, to the exclusion It Wlll be understood that if the piezoelectric device of this invention were so arranged that its vibratory eriod could be varied as found desirable, t e frequency of the oscillator to which it is connected would be similarly varied, as would also the frequency of the harmonic produced by the harmonic roducer. The piezo-elect-rlc device woul at the same time, maintain the oscillations of that harmonic constant in fre uency within very narrow limits.

1g. 2 shows an oscillator 0 connected to a similar harmonic producer of the duplex type shown in Fig. 1 for roducin odd harmonics of the frequency 0 the osci lator,

and, more articularly, any desired odd harmonic, to t e exclusion of all other odd harmonies. The circuit of the harmonic producer of 2 corresponds to the circuit of the harmomc producer .of Fig. 1 when the switch S- closes contact 6.. It will be fairly obvious that a plurality of odd harmonics are produced by this arrangement, and that any one of these harmonics may be selected by manipulation of the variable condenser D, and transmitted to the output circuit connected to the leads or conductors M, to the exclusion of all other odd harmonics.

Fig. 3 shows a harmonic producer for producing an even harmonic of the fund mental frequency of an oscillator O. In this arrangement, the plates of the vacuum tubes V, and V are in parallel relationship with each other, and are supplied with the proper plate potential by a battery B; through an inductance L Any one of the even harmonics may be selected by manipu-,

lation of the variable condenser D The selected even harmonic is transmitted to the iao inductance L and then to the output cir= cut connected to the leads M.

While this invention has been shown in certain particular embodiments, merely for 5 the purpose of illustration, nevertheless the principles of this invention may be applied to other and widely varied organizations without departing from the spirit of the invention and the scope of the appended claim, What is claimed isf The combination of two three-element vacuum tubes, a resistance interconnecting the grid electrodes of said vacuum tubes, a source of alternating current of fundamental frequency coupled to said resistance, a winding, means to connect the plate elec trodes of said vacuum tubes in parallel re lationship with each other and in series relationship with said winding whenever even harmonics are desired, means to connect the plate electrodes ,of said vacuum tubes in series relationship with each other and with said winding whenever odd harmonics are desired, means for rendering said winding selective to any predetermined odd or even harmonic, and a piezo-electric device coupled to said source to maintain its frequency constant as well as the harmonic selected by said winding. In testimony whereof, I have signed my name to thisspecification this 28th day of October, 1926.

RUSSELL S. OHIA 

